OBJECTIVES: (1) The completion of the phase equilibria and fine structure of gut luminal lipid phases important in the digestion and absorption of fat; (2) Further studies on the role of mucus glycoproteins secreted by the gallbladder in both cholesterol and pigment gallstone forming animals, i.e., the prairie dog cholesterol-gallstone model and the Deer Mouse pigment stone model. (3) Completion of phase equilibria studies on unconjugated and unconjugated bilirubin in bile and commence correlation studies on the Deer Mouse pigment stone model; (4) Pathophysiological correlation with normal and abnormal fat digestion and absorption in man; (5) Continue studies on the nucleation of cholesterol and bilirubin from supersaturated bile by mucus glycoprotein gels and the development of inhibitors of mucus synthesis and/or secretion and their use in the prevention of gallstones; (6) Continue studies by quasielastic light scattering spectroscopy to define the "structure" of native bile.